Systems presently used for the reduction, classification and concentration of crystalline mineral products require a plurality of steps and in many cases sophisticated and costly equipment. Normally, the present reducing and classifying apparatus incorporate a grinder or shredder which is initially used to reduce the size of the material to be classified. Thereafter, the material is carried by either a liquid or air medium and separated according to weight as the material is discharged or dropped from the flow stream. Lighter components are carried by the flow stream further than heavier particles and are discharged or dropped from the flow stream at a different location. Such a reduction and classification system is disclosed in U.S. Pat. No. 3,856,217, issued Dec. 24, 1974 to J. C. Brewer.
While such systems have met with some success, it will be appreciated that these units require elaborate grinding structures which initially reduce the size of the material to be classified. Moreover, classification of the units is inexact in that the materials are not clearly separated by the process. On occasion, heavier components will be carried with the flow stream to more remote discharge positions, while lighter materials may fall from the flow stream at an early point in the process and be improperly classified with the heavier or larger particles of material.
In view of the significant equipment necessary for the reduction and classification process such as that shown in the Brewer patent, these systems are not normally portable but must be assembled and operated in one location. Thus, these systems do not reduce the expense and time involved in transporting the materials to be reduced and classified to the site of the reduction and classification units. Often, the expense of transporting such materials to the treatment facility represents a sizable portion of the cost involved in the reducing and classification process.
In other systems, where a shredder or reducing mechanism is not used, the use of an air classification system is rendered almost unusable in that classification of material having naturally large or heavy components cannot be carried to any significant degree by an air flow system. In these systems, other mediums such as fluids are required, thereby adding to the complexity and expense not associated with air classification systems using an air medium only.
Classification of crystalline mineral products has normally required the use of certain chemical treatments in the final concentration process. Where such chemical treatment is required, the potential for environmental contamination is introduced. Additionally, an added cost, both by way of the cost of chemicals involved and additional equipment required to handle such chemicals, is introduced by such systems.
Thus, the need has arisen for a relatively low cost reduction and classification system which is capable of high volume production, as well as applicable to reduction and classification of a wide range of minerals and brittle noncrystalline materials. Moreover, the need has arisen for such a system which is portable and one that eliminates potential environmental hazards normally introduced by the requirement of chemical treatment in any phase of the process.